For a brief period in the 1970s and early '80s, the U.S. tried to switch over to the metric system, despite objections from real Americans that it was "Communist" or an "Arab plot." Metrication didn't get very far, but one highway remains: Arizona's Interstate 19.

Other stretches of road occasionally give directions in kilometers, but I-19—which stretches 63 miles, from Tucson to the Mexican border—is the only highway in the country that does it exclusively, across its entire length. The signs were put up as part of a Carter administration plan intended to convince Americans to make the switch, the AP wrote this week, and they may eventually be changed back to miles:

Some who agree with Rodriguez took a shot at changing the signs four years ago when the state, which oversees them, received $1.5 million in federal stimulus funding.

The Arizona Department of Transportation at the time said the signs were outdated and needed to be replaced with ones that are brighter and easier to read. "You get wear and tear on them. Obviously, they're out in the heat in Arizona. Eventually we're going to have to replace those signs," spokesman Dustin Krugel said.

They also said the new signs would be in miles.

Local business owners objected: some advertise their location using I-19 kilometer-markers, which would be altered, and others pointed to tourism from Mexico, which generates $1 billion per year in the area. (Mexico, like just about everyone else, uses the metric system.) The plan did not go forward.

The signs still need to be replaced, an Arizona Department of Transportation spokesman told the AP, but the department lacks the funding to do so now, and will seek "community feedback" before making any future changes. For now, the kilometers remain, much to the chagrin of at least one guy. "When I'm driving, I definitely can't do that math," 24-year-old Rio Rico resident Nick Rodriguez told the AP.

[h/t The World's Best Ever, image via AP]